1. Field of the Invention
Direct injection on engines with spark ignition automatically involves the process of stratified charge combustion which offers an alternative to the combustion processes called "lean mixture" by preparation of the mixture upstream from the intake valve or valves.
2. Background of the Related Art
The combustion chambers of engines with stratified charge are two types: secondary chamber and open chamber. Very numerous efforts have been conducted by designers from the world over, the most famous for the so-called open-chamber engines perhaps being those of the PROCO processes developed by FORD.
To be able to provide the conditions for correct combustion in the open-chamber stratification process, the latter being in the piston for a four-cycle engine or in the cylinder head for a two-cycle engine, the injection system and mainly the injector should have three essential qualities:
1. An ability to assure an excellent atomization of the fuel,
2. An ability to allow the penetration of the fuel jet into the chamber adapted to the conditions of engine speed and load,
3. An ability to deliver very small amounts of fuel in a stable and repetitive manner.
It has been known for a long time that the use of sonic phenomena gives an excellent atomization of air or gas and fuel mixtures, the gas pressure, being referenced either by its ratio to the manifold pressure (partial vacuum) or by its ratio to the cylinder pressure at the moment of injection, at a ratio close to 2. More recently, and in the case of development of an injection system for a 2-cycle engine, the ORBITAL company (Australia) has developed such a system, claiming such atomization.